FIG 4.

Bacterial coinfection modulates antiviral serum Abs but not anti-S. pneumoniae serum Abs. Serial bleeds from mice in indicated groups were collected and analyzed for PR8-specific IgG (A) and S. pneumoniae-specific IgG (B) by ELISA (n = 6 mice/group for infected mice and n = 2 naive mice). (C) Sera were collected on days 34 to 35 p.i. with PR8, and virus-neutralizing Abs were determined by HI assay. The kinetics of PR8-HA-specific serum IgG (D) and C12 idiotype (Id) Ig (E) in PR8- and coinfected mice. All results are from at least n = 6 mice/group. (F) PR8-specific IgG and IgA in BAL fluid of PR8 and coinfected mice (n = 5 to 12 mice/group) 10 days and 34 days after PR8 infection. Significance was determined by Student's t test. ns, nonsignificant; *, P < 0.05; **, P < 0.01; ***, P < 0.001.